How to force SSL and TLS for a perfect installed server

How can I force all mail connections to go through SSL and TLS for a server based on Ubuntu 9.04 and ISPConfig 3? Server was setup based on the tutorial provided by Falko.

I now that one can shut down the courier-pop and courier-imap service and just leave the ssl version of these services up and running, but I am looking for a better solution which will work even after a new start of the machine.